A. Field of the Invention
The present invention relates to safety astragals for elevator fire doors and more particularly to safety astragals designed for use on horizontally divided, vertically moving freight elevator fire doors and fire doors for vertical conveyors.
Freight elevator fire doors are typically comprised of two separate vertically moving sections, which are positioned between vertically disposed guide rail members which are attached on walls forming the elevator shaft. The door sections are guided in their vertical opening and closing movements by guide means attached to the vertical edges of the door sections which cooperate with and engage an inwardly extending flange member of the guide rail assembly. In opening and closing movements, the door sections move in a vertical plane in opposed relation to each other, which movement is controlled by flexible connecting members secured to each side of each door section with the flexible connecting members running over respective sheaves members secured to the guide rail assemblies.
Elevator fire doors of the counterbalanced type are conventionally used at elevator landing openings to prevent the spreading of fire between floors of a building by communication through the elevator shaft. In order to provide a fire-tight seal between the two door sections when closed, it was at one time common practice to provide a structural steel angle section on the upper door which overlapped the lower door, when the doors were in the closed position. The angle section prevented fire from passing through any space which might have existed between the doors and also prevented the introduction of objects between the doors for deposit or discharge into the shaftways. The fire seal angles, however, while they were suitable for providing a fire-tight seal, introduced a hazard upon closing the doors, since the angle also functioned as a guillotine which would tend to shear off anything left in between the doors. The steel angle sections were particularly dangerous to fingers, hands, wrists, or feet of persons who did not take sufficient care to avoid injury. The overlapping angle astragal also projected into the doorway 2 or 3 inches. Thus, if an elevator required an unobstructed vertical opening of 7 feet, a framed masonary opening of 7feet 2 inches or 7 feet 3 inches would have to be provided. Many architects and end users were not cognizant of this downward projection thus ending up with an unobstructed opening insufficient to permit the passage of loads having certain popular heights.
B. Description of the Prior Art
A variety of astragals fabricated from various fireproof materials have been proposed. Earlier safety astragals consisted of a cylinder fabricated from wire-reinforced, neoprene-coated asbestos and are described in U.S. Pat. No. 2,923,984, Canadian Pat. No. 524,866 (issued May 8, 1956) and elsewhere. Such cylindrical astragals employed spring-like reinforcing members within the astragal as functional elements employed to mount the astragal on the elevator door. In order to obtain Underwriter's approval of elevator doors, the doors with the astragals mounted thereon must be subjected to rigorous tests both as to their fire-resisting qualities and also their resistance to disintegration by the hose stream test which is applied immediately after the fire test. Since the forces employed in closing freight elevator doors are of 35 to 50 pounds, in order to produce a neoprene-asbestos fabric cylinder which will withstand repeated stresses and compression to seal, it is necessary to build a thick and strong cylinder. It has been found that when cylindrical astragals are fabricated to specifications which produce adequate fire protection and resistance to physical stresses, they are not easily compressed. These conditions are due to aging of a comparatively rigid hose-like structure. It has also been found that many injuries can occur when a finger or hand or other limb is caught between the lower sill and the astragal. Even in those cases where there is no metal-to-metal contact, serious injury can take place.
U.S. Pat. No. 3,943,663 describes an astragal fabricated by sewing together two layers of flexible fireproof material with heavy cotton thread which was then formed into an envelope around a contiguous solid mounting bar. Envelope astragals fabricated from two layers of fire-resistant material, while reducing the possibility of injury, are difficult to manufacture in an absolutely uniform cross-section. Because of the difficulty in fastening the envelope material on the mounting bar in a uniform manner, the height of the astragal is not always uniform on the envelope astragals. As a result the envelope astragals, such as disclosed in U.S. Pat. No. 3,943,663, show a tendency to be somewhat uneven and buckle slightly, which in turn causes difficulty maintaining sufficient force on the envelope to produce an effective fire seal between the astragal and trucking sill or the lower panel. Increasing the latching force does not necessarily overcome deficiencies in the sealing properties resulting from buckling or rippling of the sealing edge of the envelope astragal. Envelope astragals also suffer from the fact that they are expensive to manufacture. These higher expenses in manufacturing are attributed to material costs and the difficulties inherent in fabricating an envelope astragal. It is particularly difficult to fabricate an envelope astragal to be of uniform character to reduce the tendency of the astragal nose to buckle.